1. Field of the Invention
The present invention relates to a design-superposing display apparatus to superpose a design onto a part of a display surface of a display device, and a vehicle display unit utilizing the same.
2. Description of the Related Art
A projection type display unit such as head-up display (HUD) has been mounted on a vehicle. The HUD displays a virtual image on a windshield and superposes the virtual image on a foreground. The displayed virtual image is information which can not be displayed on a meter unit due to limited space therein. JP-2002-293162-A discloses a liquid crystal display (LCD) and a vacuum fluorescent display (VFD) as a display device for a HUD apparatus.
The colors of green, red, and blue are available for the VFD. Maximum luminance and lifetime of the respective colors is different. Only green has a required luminance for the HUD apparatus.
FIGS. 10A and 10B show a conventional VFD 100. A design W is formed in a display plane 101 transparent to a light emitted from an LED backlight 110 having a diffusion portion 112 and an LED 111.
The backlight method needs a space in a rear of the VFD 100. A heat sink is usually attached to a rear surface of the high luminance VFD 100. It is preferable to make a large contact area between the VFD 100 and the heat sink. The backlight method reduces the contact area due to a window in the heat sink to allow passage of the LED light, causing reduction of heat dissipation.